If those two rides are departing the park then it's no great loss in my opinion. Flying Dutchman is inoffensive, but nothing special. Pandemonium, however...good riddance! It's hardly one of Fabbri's best products. Lifting the whole ride structure before it can start its cycle instead of dropping the floors under the arms seems like an odd engineering decision, and I've only ever known going on it to be a miserable headrush-fest.
I'm both hopeful and unsure about the prospect of Drayton getting a coaster, because as Dan said, historically they haven't been brilliant at choosing them. If a thrill coaster is on the cards I think they really need to get it right this time, and if they do I'll visit much more regularly, as for me a good thrill coaster is what the place really lacks.